The goal of the proposed research is to couple a compact tunable ultraviolet (UV) laser system with a compact jet-REMPI time-of-flight mass spectrometer in order to provide a fieldable system for real-time concentration measurements of vapors from volatile hazardous species over contaminated sites. By allowing rapid vapor phase measurements in a matter of seconds, this technique provides real-time continuous monitoring of hazardous waste site remediation progress, and facilitates rapid mapping of waste distribution within a site, without the need for lengthy excavation and analysis of multiple soil samples. In addition, the time-varying exposure of neighboring communities to hazardous air pollutants out-gassing from the site can be monitored as out-gassing rates within the site change due to environmental conditions and waste plume migration. The jet-REMPI technique has already proven a powerful technique for measuring a variety of hazardous air pollutants with excellent sensitivity and chemical specificity in the laboratory. By coupling molecular mass measurement with optical spectroscopy, the technique can provide accurate measurements even in complex mixtures of multiple pollutants such as those found in real-world sites. The Phase I targets of his project will take this promising technology from the laboratory and yield a device that can make meaningful field measurements.